As set forth in the 3rd Generation Partnership Project (3GPP), an IP Multimedia Subsystem (IMS) provides a common core network having access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. The IMS architecture is initially defined by the 3GPP to provide multimedia services to mobile subscribers over an IP network. IP networks have become the most cost savings bearer network to transmit video, voice, and data.
IMS uses the advantage of IP networks to provide multimedia services for IMS subscribers on an IMS platform. The signaling used within IMS networks is SIP protocol. IMS defines the standard SIP interface between application servers, the IMS core network (CSCF), the IMS subscriber, the IMS database (HSS), and IMS billing elements. These standards can reduce the network integration costs and let the subscriber enjoy more stable services.
On the IMS platform, the traditional supplementary services, such as call forwarding, conferencing, and call waiting could be available for IMS subscribers. Also, many new data services, such as instant messaging, video calls, video on wait, and web-based services, will also be available for the IMS subscribers.
Providing efficient IMS online charging for operator revenue generation is important to the successful deployment of IMS networks. Several 3GPP technical specifications describe charging for IMS networks. For instance, the structure of the charging specifications of 3GPP TS 32.240 V7.0.0 (2006-09), which can be found at http://www.3gpp.org, is shown in FIG. 10.
FIG. 11 provides an overview of the logical ubiquitous charging architecture and the information flows for offline and online charging. The common charging functions are detailed further in FIG. 12 for offline charging and FIG. 13 for online charging.
FIG. 11 includes all network elements/systems (top to bottom: CS-NE all the way through to the TPF) for which charging is defined within 3GPP standards. The arrows indicate logical information flows on the Rf, Wf, Ga, Bx, ISC, Ro, Wo, CAP, and Gy reference points.
FIG. 12 provides an overview of the offline part of the common charging architecture. The figure depicts the logical charging functions as well as the reference points between these functions and to the Billing Domain. The abbreviations in the figure have the meanings respectively as follows: CTF: Charging Trigger Function; CDF: Charging Data Function; CGF: Charging Gateway Function; BD: Billing Domain, which may also be a billing system/billing mediation device.
The Charging Trigger Function (CTF) generates charging events based on the observation of network resource usage. In every network and service element that provides charging information, the CTF is the focal point for collecting the information pertaining to chargeable events within the network element, assembling this information into matching charging events, and sending these charging events towards the Charging Data Function. The CTF is therefore a mandatory, integrated component in all network elements that provide offline charging functionality.
The Charging Data Function (CDF) receives charging events from the Charging Trigger Function via the Rf reference point. The relationship between CDF and CTF may be 1:1 (integrated CDF) or 1:n (separated CDF). It then uses the information contained in the charging events to construct Charging Data Records (CDRs).
The results of the CDF tasks are CDRs with a well-defined content and format. The content and format of these CDRs are specified per domain/subsystem/service in the related middle tier charging specification (e.g. 3GPP TS 32.250 [10] for the CS domain and 3GPP TS 32.251 [11] for the PS domain, etc,).
The CDRs produced by the CDF are transferred immediately to the Charging Gateway Function (CGF) via the Ga reference point. The CGF acts as a gateway between the 3GPP network and the Billing Domain. It uses the Bx reference point for the transfer of CDR files to the BD. The entity relationship between the CDF and the CGF is m:1, i.e. one or more CDFs may feed CDRs into a single CGF.
FIG. 13 provides an overview of the online part of the common charging architecture. The figure depicts the logical charging functions in the network and the OCS and the reference points between these functions. The abbreviations in the figure have the meanings respectively as follows: CTF: Charging Trigger Function; OCF: Online Charging Function; ABMF: Account Balance Management Function; RF: Rating Function.
The traditional telecommunication charging system can be divided into two domains: prepaid and postpaid systems. The prepaid system is a kind of charging service for a subscriber who firstly purchases the access and airtime prior to use. The IN-based prepaid charging is used to real-time monitor the airtime usage, which is purchased by the prepaid subscriber in advance. The postpaid system is a kind of charging service to allow a subscriber to firstly use a network before the payment to the network usage. IT-based postpaid system is used to collect and rate the subscriber's call data record (CDR) in batch mode, and generate the postpaid subscriber's bill and invoice.
3GPP, from another angle, divides the charging systems into online charging system and offline charging system. For the offline charging mechanism, charging information does not affect, in real-time, the service rendered. For the online charging mechanism, the charging information can affect, in real-time, the service rendered and therefore a direct interaction of the charging mechanism with session/service control is required. The 3GPP doesn't limit that online or offline charging must be the prepaid or post-paid payment. The online charging can be prepaid or post-paid, and offline charging can be prepaid or post-paid payment, too.
The 3GPP charging specification only defines the basic online/offline charging framework for various networks. The multiple IMS charging system inter-working is never mentioned in these specifications, such as multiple online charging system (OCS) inter-working for group charging, charging gateway function (CGF) and OCS networking for offline and online charging convergence, charging trigger function (CTF) with multiple OCS and multiple charging data function (CDF) inter-working, etc. In a multiple charging system, how to manage the charging locations of these subscribers is performed by a distributed group charging server.
In an existing market, either in the online/offline system or in the prepaid/post-paid charging systems, all subscribers or end users are regards as individuals by mobile operators. The end user individually subscribes mobile services, manages its own account, and pays mobile service usage.
In competitive telecommunication market, most of operators have great challenge to extend subscriber base, increase revenue, reduce customer churn, and save customer acquisition, operation and maintenance cost. To breakthrough the individual service subscription market drawback, some operators are trying to position the subscribers as group, and are seeking to bundle or cluster subscriber together to provide advanced real-time usage and cost charging plan, but these subscribers charging profile is distributed in multiple charging system. For illustration purpose, the following two examples are for the distributed charging services.
Intra Class of Service Charging
When subscriber A (sub A) makes a call to subscriber B (sub B), if sub A and sub B belongs to the same class of a server, the sub A's call charge will have some discount for the intra class of service call. Sub A's account profile is provisioned in OCS 1 (e.g. located in New York), while Sub B's account profile is provision in OCS 2 (e.g. located at Chicago). OCS 1 needs to communicate with OCS 2 to query subscriber B's class of service in B's account profile to determine whether sub A and sub B belong to the same class of service.
Distributed Family Plan
A group of family members are distributed over multiple OCSs. For example, the child's account profile is provisioned in an OCS located in Milan, and the parent's account profile is provisioned in an OCS located in Roma. When the child wants to share the parent's balance or bonus, the OCS with the child' account profile needs to communicate with the OCS with parent's account profile to get parent's balance and bonus.
The prior art work in 3GPP standard specification set doesn't define how to implement the distributed IMS charging, such as CGF and OCS inter-working, multiple OCS inter-working, etc. And the existing solution for charging have both the technical and business disadvantage for this distributed IMS charging. This invention shall fix the standard gap for above problems.
The index service solution is a first-ever seen solution to realize the centralized management of charging system addresses. This invention enables an operator to manage the subscriber's charging location information for distributed charging services in a centralized index server, instead of provisioning the charging locations in each separated IMS charging system. This invention greatly saves the operator's management cost of charging.